Process of bleaching paper and fabrics



"stares JOHN G. maxim, or mnenrmm PARK,

I a NEW lfERSEY, Assieiwon T WALLACE a TIEBNAN co. me, or BELLEVILLE, NEW JERSEY, A qonroaa'rron or new You.

Processor nnmcmne PAPER Am) nannies.

To all whom it may concern:

a citizen of the United States of America, residing at Ridgefield Park, county of Bera gen, and State of New Jersey, have invented certain new and useful Improvements m Processes of Bleaching Paper and Fabrics,

of which the following is afull, clear, and exact description.

a The invention, subject of mypresent application for Letters Patent, is a new and improved process of bleaching such materials as the fibres of paper pulp, and for a clear understanding of its nature, a brief review of the methods'heretofore followed in such caseais apposite. I

' In one method which has been practiced in this art, the result has been largely accomplished by subjecting the fibres in the form ofpulp to the action of an aqueous s0- lution of bleaching powder, which is composed essentially of calcium -hypochlorite containing varying ,amounts of I dissolved calcium hydroxide. These and like solutions, however, are notably slow in their bleaching action and to hasten or promote such action heat has usually been applied,-

but it is often the case with this process that great difficulty has been experienced'in obtaining satisfactory colors by the use of such solutions.

When .such difiiculties arise, the use of, excessive amounts of avallable chlorine has been resorted to inorder to accomplish the 85 desired results, and in other casesnotably as set forth in the patents'to Ornstein Nos. 1,298,553, and 1,298,554 and 1,298,555, it has been prop'os'ed to overcome the same objections by extreme dilution or by certain re- 40 actions which have never proved capable 'of very extended practicable orcommercial application, being somewhat theoretical in character. It is believed from the results of experimental investigation of the processes 4 5 set forth in these patents, that economies in operation by their use can only be secured when small amounts of chlorine are required to bleach such. fibres as rags, or old bleached paper. In the case of sulphite wood pulp,

bleaching vat;

. H esparto' hemp or soda wood ul no a Be it known that I, J OHN CLARk BAKER, 7 p p p Another method adopted tospeed up the bleaching action and secure greater economy in the'process has been to use alum in the This, however, while a wldely'used plan and entirely successful in as ultimate results, is expensive and dim- Specification of Letters Patent. -Patemitedl Apr. 118, 11.922. i Applicationfiled rum is, 1921. Serial 1%. 485,701.

cult'to control, besides which it leaves aluminium oxide in the finished aper.

Another plan looking to t e accomplishment of the same results has been to add sulfuric acid to the vat in addition to the calcium hypochlorite. This-produces. a violent reaction or effect and is, moreover, liable to.

injure'the stock by rendering it tender, or

burning, besides which it releases free b clzlorine. 7

Still other methods that have been e it- Y tempted or proposed for securing the desired results are'set forth in the British Patent No. 11,333'01 1884, which involves the use of acetic acid; 'a suc'cessfulbut expensive proceeding, and also-in British Patent No. 595 ,of 1883, which contem lates the continued use of calcium hypoch orite and carbon dloxlde, a plan involving great dif- I ficulty. I r v In an a plicationffiled' by Wallace and Baker on pril24, 1920, Serial No 376,224,

is described a process of producing hypochlorite solution. bythe instantaneous and continuous admixture of a solution of a base with chlorine, and in a series of experiments with this process of making bleaching solu-,

because of the presence ,of impurities from the base, in case lime were used, which had .to be settledout before use, and by reason -of the unstability of the solution, it was not-practicable to economically use the process with'lime. l

I then discovered that if neutral or slighttions I discovered that if a larger proporly alkaline stable solutions were first pre-.

pared, settled and the clear liquor assed through the apparatus with the additlon of chlorine gas equivalent in amount to agproximately 5 to per cent of the. avai able chlorine in the solution, solutions were produced which, if used immediately, contained all of the original chlorine-as well as that added, and that they possessed remarkable bleaching properties; that the process of bleaching was much more rapid than before; that the final colors obtained were. much whiter than those produced by ticable embodiment of my present invention.

In carrying out this process for bleaching purposes, the hypochlorite solution in 1:} per cent to 4 per cent concentration is added to the pulp to be bleached and either simultaneously or afterits introduction into the vat the desired amount-0f chlorine water is added to the pulp. At any practicable temperature this method of bleaching is preferable to that involving the use of neutral or alkaline hypochlorite solutions, but even better'results are secured at the somewhat higher temperatures of 100 and 110 F.

The presence in the bleach of the additional chlorine may be obtained in either of two ways: First, chlorine gas may be added to a settled solution of hypochlorite by instantaneous contact such as practiced in the process of the Wallace and Baker application above referred to, but in this case the resulting solution must be used immediately for bleaching. Second, an aqueous solution of chlorine water may be combined with the solution of hypochlorite.

These two solutions may be produced in any known and preferred manner and are used. either by admixture with each other in the required amounts to give the desired ratio between the two forms of chlorine, and used immediately after mixing, or the two solutions may be passed simultaneously into the bleaching vat, or finally the two solutions may be passed into the vat successively.

The first described method of introducing the chlorine gas with the hypochlorite solu tion has the advantage that'it requires the minimum amount of dilution of the pulp in order to obtain the bleach. The second concentration 0 amount of l1me'1n excess, the temperature,

method which involves the use of the two solutions, has a disadvantage in that it re quires a larger volume or dilution than the first butit has the compensating advantage that the proportions of the agents may be much more readily varied as needed, and

also that the. solutions are both relatively stable before they are brought together. This greatly simplifies the plant control of the operation.

The reactions that occur in this process may be thus stated oaocl more, 201 H,o CaOO1, can 2HOO1+ H2O.

In the reactions as above written the amounts of each constituent required are not indicated, as this depends upon the of the hypochlorite, the

and the desired amount'of hypochlorous acid in the final solution. x

All variations desired in the bleaching may be controlled by the relative amount of chlorineadded. The most important factor is the amount of HOCl in the solution, as in bleaching the results are largely due to this agent, which, however, should be present in the minimum amount to yield the desired color, speed and economy of operation, v i

- As the bleaching proceeds the reactions which occur are:

HOCl- O (acts on color) HCl. CaOCl HCl CaCl HOCl.

keeping always a small, but constant, amount present during the bleaching. The presence of large amounts of this acid is to' be avoided as other reactions occur with the materials described, rendering them difiicult to bleach.

Having now described my invention what I claim is 1. A bleaching solution which consists of a solution of a base containing chlorine to an amount in excess of that required for neutralizing the same.

2. A bleaching solution consisting of a neutral hypochlorite solution containing an excess of chlorine.

3. A bleaching solution consisting of a neutralhypochlorite solution containing an excess of chlorine to the amount of ten per cent of the available chlorine in'the solution.

4. The method of bleaching herein de scribed which consists in introducing into the bleaching vat a neutral hypochlorite solutionand an excess of chlorine over that scribed which consists in simultaneously inavailable in the solution. troducing and mixing in the bleaching vat 5. The method of bleaching herein dea neutral hypochlorite solution, and a solu- 10 scribed which consists in introducing into tion of chlorine and water. 1 the bleaching vat a neutral h'ypochlorite In testimony whereof I hereto aflix my solution and a solution of chlorine in water. signature. v 6. The method of bleaching herein de- JOHN C. BAKER. 

